Until now, the splitting of fatty acids by hydrolysis from glyceryl esters components of vegetable oils only occurred at a temperature of 250° C. and 49 kg/cm2 of pressure (milled process) as an hydrolytic process to produce fatty acids as raw material to manufacture toilet soap from vegetable oil and animal fats, using only a one percent catalyst generally sodium or potash hydroxide (NaOH or KOH). FULLER wrote, “Over the years, fatty acids have been produced by four basic processes, i.e., saponification of fats followed by acidulation, the Twitchell Process, batch autoclave splitting, and continuous high-pressure, high temperature hydrolysis.”
The production of methyl or ethyl esters is presently the result of transesterification (interesterification) whereby any vegetable oils are mixed with an excess of anhydrous alcohol in 1:6 ratio with one to two percent catalyst, generally sodium or potash hydroxide (NaOH or KOH) or sodium methoxide (NaOCH3), resulting in methyl or ethyl esters (biodiesel), glycerol (C3H5(OH)3) and alcohol dissolved by water process and recovered by azeothropic distillation and dehydration with benzol when ethanol is used.
The process of transesterification is well known throughout the world for some time. ALVIM quoted LOURY and MENSIER indicated that since 1945 many had already studied the production of methyl and ethyl esters of fatty acids through transesterification. The current process for the production of toilet soaps from fatty acids used by Procter & Gamble and Colgate Palmolive (milled process) patented between 1935 and 1940 used the splitting of fatty acids and glycerol with a continuous process of hydrolysis in insulated towers at high temperatures with superheated steam (240° C.) at high pressure (49 kg/cm2) in a counter flow for two to three hours.
The production of fatty acids by splitting in Europe was processed in an autoclave where the mixture of oil and water was submitted to temperatures of 250° C. at 10 kg/cm2 in a batch process for five to six hours. Another process known in the United States as the TWITCHELL process is no longer used. This is also a batch process whereby the oil and water is mixed with 0.1 to 0.2 percent of sulfuric acid for 36 to 48 hours and saturated steam at atmospheric pressure. This process was used primarily before the Second World War.
The chemical principle of transesterification is that the two reactions hydrolysis and esterification occur in a single step in a unique two-phase reaction. Many problems may arise from the transesterification process when using ethyl alcohol and not methyl alcohol, due to the tendency of the organic reaction to reverse in the second phase when carried out in the batch process. The yields drop to 60 percent of ethyl esters. Many researchers try to reduce the reverse tendency of this reaction by looking for catalysts other than sodium hydroxide or sodium methoxide. Some of these catalysts are expensive, somewhat rare or may need to be synthesized.